[isThereClarity]

From my understanding of that abstract, it's the _pre-agricultural_ erosion rates are lower than assumed, so the tolerance value for agricultural land has been set too high.

From the conclusion:

> We find that pre-agricultural erosion rates in the midwestern United States are on the order of 0.0001–0.1 mm yr–1. Soil loss tolerance values of 1 mm yr–1 are one to four orders of magnitude higher than pre-agricultural erosion rates. Similarly, the agricultural erosion rates are 10–1000 times greater than the preagricultural erosion rates. Our results indicate that tolerable soil erosion, as currently defined, will lead to the depletion of midwestern soils.